Turbine engines, and particularly gas or combustion turbine engines, are rotary engines that extract energy from a flow of combusted gases passing through the engine onto a multitude of rotating turbine blades.
Gas turbine engines for aircraft, for example, are designed to operate at high temperatures to maximize engine efficiency, so cooling of certain engine components, such as the high pressure turbine, can be beneficial. Typically, cooling is accomplished by ducting cooler air from the high and/or low pressure compressors to the engine components that require cooling. Temperatures in the high pressure turbine are around 1000° C. to 2000° C. and the cooling air from the compressor is around 500° C. to 700° C. While the compressor air is a high temperature, it is cooler relative to the turbine air, and can be used to cool the turbine.
Contemporary turbine airfoils generally include one or more interior cooling passages for routing the cooling air through the airfoil to cool different portions, such as the walls of the airfoil. Often, film holes are used to provide the cooling air from the interior cooling passages to form a surface cooling film to separate the hot air form the airfoil. However, the film holes provide the surface cooling film to a discrete, local portion of the airfoil and require a large flow to maintain proper surface cooling over an area of the airfoil exterior surface.